"Surface Key Assumptions" is the first step in the "What Wows" stage of Jeanne Liedtka's 15-step Design Thinking methodology. This step involves moving from idea generation to idea testing. Three testing techniques are suggested: thought experiments, field experiments, or market experiments. This 17-minute video is part of the Design Thinking video series meant to accompany any one of three cases (Arena Industries [UVA-S-0240], Trenton State College [UVA-S-0241], or Great Lakes [UVA-S-0248]) that explore the design thinking approach to innovative problem solving.